1. Field of the Invention
The present invention relates to a trim cover assembly for use with a vehicle-seat-related product including a vehicle seat and a headrest, the trim cover assembly having a highly soft cushion portion (a thick foam wadding layer) for receiving a body portion of a user or seat occupant, thereby providing an improved touch and comfort to the user or seat occupant. In the case of a headrest for instance, the trim cover assembly as applied to the headrest is provided with a highly soft cushion portion (a thick foam wadding layer) for receiving a head of a user. Also, the present invention relates to a sewing method for forming such sort of trim cover assembly by use of a sewing machine.
2. Description of Prior Art
Most of hitherto ordinary trim cover assemblies used for vehicle seats, headrests and so forth is of a three-layer lamination structure comprising: a surface cover material; a foam wadding; and a wadding cover, in this order, which is for example disclosed from the Japanese Laid-Open Patent Publication 63-35314 (JP 63-35314 A). Namely, the surface cover material, which faces exteriorly of the trim cover assembly, may be formed from a textile fabric, a synthetic leather or the like. The foam wadding is bonded at one surface thereof to a reverse side of that surface cover material in an integral manner, as by fusing. And the wadding cover, which may be made of a film of synthetic resin, an unwoven cloth material or the like, is bonded to another surface of the foam wadding, opposite to the foregoing one surface of the foam wadding bonded to the surface cover element. In general, a thickness of this trim cover assembly of three-layer lamination structure is not more than 10 mm.
In a practical process for forming a vehicle seat or a headrest, a desired configuration of trim cover assembly sized to cover the seat or headrest is formed by providing a plurality of cover materials of the aforementioned three-layer lamination structure, wherein the cover materials have been obtained by cutting one piece of base cover material of the same three-layer lamination structure into a required number of cover materials in advance, and then sewing together such plurality of cover materials, while aligning the corresponding ends of them with each one another. In that way, a desired configuration of trim cover assembly is formed. Finally, such trim cover assembly is affixed substantially on an entire surface of a foam padding provided on an internal frame of a vehicle seat or a headrest, so that a resultant vehicle seat or headrest is obtained.
Recently, with regard to a headrest for example, it has been desired that a portion of the headrest, on which a head of seat occupant or user is to be contacted, should be increased in softness and pliability to provide a highly improved soft touch of the headrest in order to give an optimal comfort to the user's head. For that purpose, in recent years, a trim cover assembly of an extremely soft property, or what can be described as “ultra soft trim cover assembly”, has been required in the field of vehicle-seat-related products including vehicle seats and headrests.
In order to obtain such extremely soft trim cover assembly, it has been found that one unitary piece of elastic foam material, or one piece of slab urethane foam, which is extraordinarily large in thickness relative to a usual thickness of the slab urethane foam found in the vehicle seat related field, is employed and simply incorporated in a conventional trim cover assembly. A required thickness of such extremely thick slab urethane foam is 30 mm, for instance. With this construction, the trim cover assembly is provided with a highly increased softness. In the case of a headrest covered with that extremely soft trim cover assembly, a far-improved comfort and soft touch are given to a head of a user.
However, in a practical process of forming such extremely thick trim cover assembly, it has been found impossible to use an ordinary sewing machine to sew together the afore-said great thickness (30 mm) of slab urethane foam (or thick foam wadding) and the previously-stated three layers, i.e. the surface cover material, the foam wadding and the wadding cover. That is, prior to sewing processes using the sewing machine, the slab urethane foam material having a thickness of as great as 30 mm is sandwiched between the foam wadding and the wadding cover, which results in a total thickness of those four juxtaposed layers being over 30 mm. According to the ordinary sewing machine used for production of vehicle seat and headrest, the pressure foot member of that sewing machine can be raised up to the order of 20 mm as an upper limit and can never be lifted above such 20 mm level. Therefore, the foregoing four juxtaposed layers of over 30 mm can not be placed under such ordinary pressure foot member of the sewing machine, thus making it practically impossible to use the sewing machine to sew the four layers together.